The present invention relates to aircraft engine thrust reverser actuation systems and, more particularly, to a decoupler that is used to limit the torque in an aircraft thrust reverser drive train that is driven by a dual output power drive unit.
When a jet-powered aircraft lands, the landing gear brakes and aerodynamic drag (e.g., flaps, spoilers, etc.) of the aircraft may not, in certain situations, be sufficient to slow the aircraft down in the required amount of runway distance. Thus, jet engines on most aircraft include thrust reversers to enhance the braking of the aircraft. When deployed, a thrust reverser redirects the rearward thrust of the jet engine to a generally or partially forward direction to decelerate the aircraft. Because at least some of the jet thrust is directed forward, the jet thrust also slows down the aircraft upon landing.
Various thrust reverser designs are commonly known, and the particular design utilized depends, at least in part, on the engine manufacturer, the engine configuration, and the propulsion technology being used. Thrust reverser designs used most prominently with jet engines fall into three general categories: (1) cascade-type thrust reversers; (2) target-type thrust reversers; and (3) pivot door thrust reversers. Each of these designs employs a different type of moveable thrust reverser component to change the direction of the jet thrust.
Cascade-type thrust reversers are normally used on high-bypass ratio jet engines. This type of thrust reverser is located on the circumference of the engine""s midsection and, when deployed, exposes and redirects air flow through a plurality of cascade vanes. The moveable thrust reverser components in the cascade design includes several translating sleeves or cowls (xe2x80x9ctranscowlsxe2x80x9d) that are deployed to expose the cascade vanes.
Target-type reversers, also referred to as clamshell reversers, are typically used with low-bypass ratio jet engines. Target-type thrust reversers use two doors as the moveable thrust reverser components to block the entire jet thrust coming from the rear of the engine. These doors are mounted on the aft portion of the engine and may form the rear part of the engine nacelle.
Pivot door thrust reversers may utilize four doors on the engine nacelle as the moveable thrust reverser components. In the deployed position, these doors extend outwardly from the nacelle to redirect the jet thrust.
The primary use of thrust reversers is, as noted above, to enhance the braking of the aircraft, thereby shortening the stopping distance during landing. Hence, thrust reversers are usually deployed during the landing process to slow the aircraft. Thereafter, when the thrust reversers are no longer needed, they are returned to their original, or stowed, position. In the stowed position, the thrust reversers do not redirect the jet engine""s thrust.
The moveable thrust reverser components in each of the above-described designs are moved between the stowed and deployed positions by actuators. Power to drive the actuators may come from a dual output power drive unit (PDU), which may be electrically, hydraulically, or pneumatically operated, depending on the system design. A drive train that includes one or more drive mechanisms, such as flexible rotating shafts, may interconnect the actuators and the PDU to transmit the PDU""s drive force to the moveable thrust reverser components.
Each of the above-described thrust reverser system configurations is robustly designed and is safe and reliable. Nonetheless, analysis has shown that secondary damage to various portions of the thrust reverser system may result under certain postulated conditions. For example, if one of the actuators coupled to one of the PDU outputs becomes jammed, it is postulated that all of the drive force supplied from the PDU would be concentrated, via the synchronization mechanisms, on the jammed actuator. This postulated condition may result in damage to the actuator system components, including the PDU, actuators, drive mechanisms, or the moveable thrust reversers components. Repairing such damage can be costly and result in aircraft down time. One solution is to use stronger components, but this increases the cost and/or weight of the thrust reverser system. Another solution is to include numerous, independently operated torque limiters or decouplers in each drive train coupled to the PDU outputs. However, this solution may also increase system cost and/or weight.
Accordingly, there is a need for a thrust reverser system that improves upon one or more of the drawbacks identified above. Namely, a system that reduces the likelihood of component damage if thrust reverser system fails, for example, by a jammed actuator, without significantly increasing the cost and/or the weight of the thrust reverser system components. The present invention addresses one or more of these needs.
The present invention provides a system and method that sequentially decouples a dual output thrust reverser system PDU assembly from its load in the event a torque magnitude is reached between the assembly and load. Thus, the present invention reduces the likelihood of component damage without significantly increasing the cost and/or weight of the system.
In one embodiment, and by way of example only, a thrust reverser control system includes a power drive unit operable to supply a drive force, at least two drive mechanisms, and at least two actuator assemblies. The drive mechanisms are each coupled to receive the drive force, and each actuator assembly is coupled to at least one of the drive mechanisms and operable to move, upon receipt of the drive force, between a stowed position and a deployed position. The power drive unit includes a motor, first and second output sections, and a deadband coupler. The motor has a shaft with at least a first output and a second output and is operable to supply rotational power to a first and a second load, respectively. The first output section is coupled to the first motor output and is operable to decouple the motor from the first load upon a torque magnitude being reached in the first output section. The second output section is coupled to the second motor output and is operable to decouple the motor from the second load upon a torque magnitude being reached in the second output section. The deadband coupler is coupled to the first and second output sections and is operable to selectively couple the first and second output sections together a time period after the first and second output sections have unequal rotational speeds.
In another exemplary embodiment, a power drive unit includes a motor, first and second output sections, and a deadband coupler. The motor has at least a first output and a second output and is operable to supply rotational power to a first and a second load, respectively. The first output section is coupled to the first motor output and is operable to decouple the motor from the first load upon a torque magnitude being reached in the first output section. The second output section is coupled to the second motor output and is operable to decouple the motor from the second load upon a torque magnitude being reached in the second output section. The deadband coupler is coupled to the first and second output sections and is operable to selectively couple the first and second output sections together a time period after the first and second output sections have unequal rotational speeds.
In still another exemplary embodiment, in a thrust reverser control system including a power drive unit having at least a first and a second output section each coupled to at least one thrust reverser movable component, respectively, a method of operating the system includes rotating the power drive unit first and second output sections to move the thrust reverser movable components between a stow and a deploy position. One of the power drive unit output sections is decoupled from its associated thrust reverser movable component upon a torque magnitude being reached therebetween. The other power drive unit output section is then decoupled from its associated thrust reverser movable component a time period after the power drive unit output sections have unequal rotational speeds.
In yet another exemplary embodiment, in a power drive unit including a motor having at least a first and a second output coupled to at least a first and a second power drive unit output section, respectively, a method of operating the power drive unit includes rotating the first and second motor outputs to thereby rotate the power drive unit first and second output sections. One of the power drive unit output sections is decoupled from its respective motor output upon a torque magnitude being reached therebetween. The other power drive unit output section is then decoupled from its respective motor output a time period after the power drive unit output sections have unequal rotational speeds.
In yet another exemplary embodiment, a thrust reverser system includes first and a second actuator assemblies, first and second drive mechanisms, and a deadband coupler. The first and second drive mechanisms are operably coupled to the first and second actuators, respectively, and are adapted to rotate upon receipt of a rotational drive force. The deadband coupler is operably coupled between the first and second drive mechanisms and is operable to selectively couple the first and second drive mechanisms together a time period after the first and second drive mechanisms have unequal rotational speeds.
Other independent features and advantages of the preferred system and method will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.